Previously, many types of box structures have been used in endeavoring to provide an effective means for producing sufficient strength to permit stacking. Many attempts have been made to add a rigid structural member in each corner of a box to support the weight loading rather than utilizing the structural rigidity of the box itself. While this ancillary element served the purpose, its expense and assembly labor requirement has not completely solved the problem. Other inventions were directed to folding material over in the corners doubling the wall thickness, however, if the stack was not completely even, the strength in the corners was not evenly distributed, again not always fulfilling the need.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention. However, the following U. S. patents were considered related:
______________________________________ U.S. Pat. No. INVENTOR ISSUE DATE ______________________________________ 2,634,021 Cella Apr. 7, 1953 3,270,943 Polenghi Sep. 6, 1966 3,935,991 Crane Feb. 3, 1976 4,174,045 Heller et al Nov. 13, 1979 4,613,045 Watson Sep. 23, 1986 4,799,670 Vilella Jan. 24, 1989 ______________________________________
Cella, in U.S. Pat. No. 2,634,021, teaches a container construction for boxes, or crates, that are fabricated of sheet metal with a reinforcing angle-piece fitted into each corner. A lug projects f rom the top of the crate to intersect with a crate stacked on the top thereof. The sides are wood and riveted to the sheetmetal ends.
U.S. Pat. No. 3,270,943 of Polenghi discloses a paperboard container utilizing triangular shaped rods of wood or other material resistant to compressive stresses. Each rod has two blind holes, one in each end, in which a projection is placed in the top, one to align and hold the box to one stacked thereabove., The paperboard is cut-away for the projection and hole.
Cranes invention in U.S. Pat. No. 3,935,991 employs molded thermosetting plastic reinforcing end frames secured to outer sides of end walls of a paperboard container body permitting stacking. Tabs interlock with the lids, or cover panels, locking them closed allowing temporary opening for display of the produce within.
U.S. Pat. No. 4,174,045 of Heller et al teaches a metallic platform with supports to receive a like platform stacked on top. Side walls consist of steel plates that engage the corners and the bottom also include feet for resting the platform away from the ground.
Watson in U.S. Pat. No. 4,613,045 discloses a paperboard container that has the corners folded into a triangular shape with the stability of the corner reinforcements provided by interlocking tabs that are folded down and threaded through apertures cut into the top panels. The resulting reinforced corner then contains a double thickness material adjacent to the sides and ends and a single proximal corner reinforcement diagonally positioned across the corner. The rigid relationships provide stability and strength to a column of containers, however, two problems exist with this prior art. First, the requirement for threading a flap through an aperture to lock the corner in place is labor intense, as the paperboard must be bent by hand when inserted and forced in flush necessitating a tight radial bend making the procedure extremely time consuming. Second, the reinforced corner has only the single diagonal weight bearing member, as the other two are contiguous with the sides and ends and offer little or no support when stacked, whereas the instant invention contains three supports directly in the corner, all of which are away from the side and end panels and are weight bearing.
U.S. Pat. No. 4,799,620 of Vilella folds and assembles the box in a conventional manner, except at the corners where pillars are constructed by superimposing a series of double panels having two or three material thicknesses. The upper portion of each pillar is connected together with a cap of plastic material the shape of a prism with a triangular base having a solid bottom and opening to receive, like parts in a similar box stacked thereupon. The weight support is augmented by the plastic cap.
It will be noted that prior art has attempted to reinforce the corner of a box container by adding a secondary structural member or a single diagonal fold in the corners, however, none of the prior art found includes a combination of diagonal and doubled angular corners that unitedly support the weight of a box stacked on top.